| タイトル | LU-HF Age and Isotope Systematics of ALH84001 |
| 本文（外部サイト） | http://hdl.handle.net/2060/20090012288 |
| 著者（英） | Shafer, J. T.; Righter, M.; Brandon, A. D.; Beard, B. L.; Peslier, A. H.; Lapen, T. J. |
| 著者所属（英） | NASA Johnson Space Center |
| 発行日 | 2009-03-23 |
| 言語 | eng |
| 内容記述 | Allan Hills (ALH) 84001 is an orthopyroxenite that is unique among the Martian meteorites in having the oldest inferred crystallization age (approx..4.5 to 4.0 Gyr) [e.g., 1-6 and references therein 7]. Its ancient origin makes this stone a critical constraint on early history of Mars, in particular the evolution of different planetary crust and mantle reservoirs. However, because there is significant variability in reported crystallization ages, determination of initial isotope compositions is imprecise making assessment of planetary reservoirs difficult. Here we report a new Lu-Hf mineral isochron age, initial Hf-176/Hf-177 isotope composition, and inferred Martian mantle source compositions for ALH84001 that place constraints on longlived source reservoirs for the enriched shergottite suite of Martian meteorites including Shergotty, Zagami, NWA4468, NWA856, RBT04262, LAR06319, and Los Angeles. Sm-Nd isotope analyses are under way for the same mineral aliquots analyzed for Lu-Hf. The Lu-Hf system was utilized because Lu and Hf are both lithophile and refractory and are not easily redistributed during short-lived thermal pulses associated with shock metamorphism. Moreover, chromite has relatively modest Hf concentrations with very low Lu/Hf ratios [9] yielding tight constraints on initial Hf-176/Hf-177 isotope compositions |
| NASA分類 | Geophysics |
| レポートNO | JSC-17947 |
| 権利 | Copyright, Distribution as joint owner in the copyright |
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